150 is 37.5% of 400.
Step 1: Translate the words into an equation.
150 | is | what percent | of | 400 |
150 | = | x | $ \cdot $ | 400 |
Step 2: Solve for $ x $.
$$ \begin{aligned} 150 &= x \cdot 400 \\[1.2 em] 400 \cdot x &= 150 \\[1.2 em] x &= \dfrac{ 150 }{ 400 } \\[1.2 em] x &= 0.375 \end{aligned} $$Step 3: Express $ x $ as a percentage.
$$ x = 0.375 = 0.375 ~~\cdot~~ 100 \% = 37.5 \% $$